The field of the invention is that of condition-responsive devices and the invention relates more particularly to pressure responsive devices adapted to be exposed to relatively high fluid pressures.
Conventional condition-responsive devices such as pressure switches have a diaphragm arranged to be exposed to an applied fluid pressure at one side of the diaphragm and have at least one dished disc element arranged against an opposite side of the diaphragm to normally support the diaphragm against the applied pressure. The dished disc element is of a conventional type having a dished central portion which is movable from an original dished configuration to or toward an inverted dished configuration with snap action when the pressure applied to the element through the diaphragm reaches a predetermined disc actuating pressure level. The dished element is arranged to move a motion transfer pin or the like during snap acting movement of the element to perform a control function such as switching electrical contacts in an adjacent device chamber. Typically the diaphragm is sealed to a device base by welding to isolate the pressure medium from the switching chamber and typically the dished disc element is adapted to return to its original dished configuration with snap action when the applied pressure falls to a predetermined reset pressure level to reset the device. Where the device is to be exposed to very high actuating pressures, a stack of the dished disc elements is arranged in nested relation to provide the support for the diaphragm. Different members of the dished disc elements are used in the stack to adapt different devices to display different actuating and reset pressure characteristics. Where the diaphragm is to be exposed to high pressures, it is desirable to provide support substantially across the full expanse of the diaphragm.
In such known devices, it is found that, when the peripheral portions of the dished disc elements move toward the diaphragm during snap acting movement of the discs, the diaphragm can be damaged so that its service life is shortened. That is, high pressures applied to the diaphragm can force the diaphragm to conform to the configuration of the peripheral parts of the stack of inverted dished disc elements and can cause excessive diaphragm material deformation at that location, thereby altering the service life and performance of the diaphragm. It is also difficult to provide such devices having durable, sealed and welded constructions in an inexpensive manner while also permitting the devices to accommodate different numbers of dished disc elements in stacked, nested relation to each other within the devices to provide devices with desired different response characteristics.